CPU Flashcards
Where does the CPU fetch instructions from?
RAM (Random Access Memory)
What does the CPU do?
The Fetch-Decode-Execute cycle. The CPU fetches instructions from memory (RAM), it decodes the instructions and then executes those instructions. The instructions are provided by a computer program.
What is the purpose of the CPU
To process data
What computer components does the CPU control?
Hard disk
DVD drive
Sound system
Graphics system
What are the 3 sections inside the CPU
Control Unit
Arithmetic Logic Unit (ALU)
Registers
What 3 jobs does the control unit do?
It controls the way data moves around the CPU
It executes the instructions provided by the program
It controls and monitors the flow of data between the CPU and other components such as input devices, memory, graphics card etc
What 2 jobs does the ALU do?
Arithmetic operation - it performs standard arithmetic operations such as addition, subtraction, multiplication etc
Logic operation - it deals with logic and comparisons such as ‘is this value greater than that value’ the answer is always either ‘true’ or ‘false’
What is a register?
A type of memory inside the CPU
What are registers used for?
Registers are used to hold temporary data while a software program is running. As the CPU processes the data, the software program will shift the data in and out of the registers
Which is faster to shift data to and from?
The registers are much faster than cache or RAM, speeding up the processing time
What are the 5 types of register?
Memory Address Register (MAR) Memory Data Register (MDR) Accumulator Program Counter Instruction Register
What are the MDR and the MAR used for?
To move data and instructions to and from main memory
What does the Accumulator do?
It’s where data is stored as calculations are underway
What does the Program Counter do?
Points to the next instruction
What does the Instruction Register contain?
The next instruction to be run
What is cache?
Is a small, but extremely fast, type of RAM
Why is cache memory used?
To speed up processing time, cache memory is used to store instructions or data that are either frequently used, have recently been used or are about to be used
Which level of cache is the fastest?
Level 1 Cache
What is Level 1 Cache?
Is the fastest but the smallest size and resides inside the CPU chip
What is Level 2 Cache?
Is a bit slower but is larger, and so can hold more data
What is Level 3 Cache
Is slower still but can hold the most data
What is the clock in the CPU?
A tiny quartz crystal that inside the CPU chip that ticks at a steady rate
What does 1 tick of the clock mean?
1 instruction processed
What clock speed does a typical computer have?
3GHz, meaning 3 Billion instructions processed every second
